Making PCB stencils with CadSoft Eagle and MoshiDraw 2013
This got me a useable stencil with the K40/ecpur style “40W” lasers
Eagle DRC using ITEADs ( doesn’t really matter which )
First shrink the tCream pads.
2 or 3mil worked in the min//max cream settings, rectangles that are part of packages aren’t affected by this setting, only auto tCream from pads.
Next switch off all layers except tCream or bCream.
Print the layer as a PDF ( requires adobe’s driver /mill). Use solid, black scale of 1, bottom left
Save that as a PDF
Load it into Illustrator, then Save it as an AI format file Version 8
Import the AI into MoshiDraw
Output to Machine
I use 10 10 speed for engrave and move. Cut just doesn’t work well, 16 speed will work, but I got the best results with a slower speed.
I did my test cuts between 30 and 45 power, 45 worked fine but 30-35 is probably better, I used dura-lay uncoated mylar sheets 4 mil. I also used air assist from a silentaire supersilent compressor.
Another way to do it, which does seem to generate a more accurate mask is to print it directly to the MoshiPrint driver, though it leaves a black bar at the bottom for me, so that has to be edited out, which you can set the page size, it seems to ignore it.
Select the MoshiPrint, and have MoshiDraw running and it’ll print it directly to the software. You can also get it it to temporarily write to a file but it’ll delete it quickly.
Printing to a BMP then editing it with a bitmap editor like Cosmigo’s ProMotion lets you go in and touch up pads that you can’t control easily in Eagle. You then import that BMP into MoshiDraw, MoshiDraw doesn’t use the same pixel to mm conversion size on Import that it does for printer driver, so you have to fix it up afterwards, the default conversion is 600 DPI so do (pixels/600) [in->mm] then set that size in MoshiDraw after its imported. Change the Destination X and Y pixel width/height to the MM conversion you do.
So for a image that’s 2000×1000 width/height at 600 DPI, you’d do
Destination X = ( (2000/600) * 25.4 ) = 84.66mm
Destination Y = ( (1000/600) * 25.4 ) = 42.33mm
The lasers smallest step is 0.025mm but the kerf of the cut is probably a lot bigger than that.
This image has a different resolution.
I believe the Chinese below “Overlay” is an aspect ratio lock
You can also just print directly from the image software to MoshiDraw, but watch out for software that halftones or dithers when it prints.
MoshiDraw does not work well with large images, above 600 DPI it really chokes.
What we really need is a smart engrave mode where the laser travels either –X X+ or –Y Y+ direction depending on the length of the engrave, so a [___] shape would cut left to right but a || cut would be up/down. MoshiDraw has an option to change the direction of the cut, but it rotates the image too, what we want is same table orientation and position, but head travels in a different direction